At present, tungsten wire doped with potassium, silicon, and aluminum and used as filaments in lamps is made by various processes giving wire with different combinations of strength and ductility. For example, 36 mil diameter wire (A) having a strength of about 48 g/mg/200 mm and elongation of about 1.5% on the average can be produced. Also, 36 mil diameter wire (B) having a strength of about 54 grams/mg/200mm and elongation of about 4% can be produced.
Wire having a combination of the strength in the range of that of A and the elongation in the range of that of B is not ordinarily produced. Wire having this combination of strength and ductility would be desirable for certain filament wire applications and for certain drawing operations to further reduce the size of the wire.